The solar-powered LED street light works on the principle of solar cells or PV cells to absorb the solar energy in the daytime. The PV cells convert solar energy into the electrical energy. The converted energy is stored in the battery and the solar street lights use solar energy. Nowadays solar street lights are available beside the roads. At the night time, the lamps start automatically and it uses the electrical energy which is stored in the battery. Every day this process continues.
Block Diagram of Solar Powered LED Street Light
The light emitting diode comprises of the chemical compound. When the direct current from the battery passes through the light, then it gives the light. Solar LEDs are available in different shapes, styles, and sizes. Generally, the lifespan of the light emitting diode is very high and it requires very little current.
The solar-powered LED street lights turn on from dusk to dawn. The LED Streetlight routinely activates after the dusk and deactivates after the dawn. The designing of the entire system includes Power Supply Block, AT89S52/AT89C51 Microcontroller, Solar Panel, LED, PWM, MOSFET, Photovoltaic Cells/Solar Cells, LM324, 1N4007/1N4148, Resistor, and Capacitor. Software requirements: Keil compiler, Language: Embedded C or Assembly.
A microcontroller is a very important device in the proposed system, used to make a decision the status of the charging and lighting by activating and deactivating. Some of the microcontrollers are pre-programmed and it includes a battery charger, a LED lamp driver, a driver, a secondary power supply, a microcontroller unit and a protection circuit. The battery can be controlled by the microcontroller from the charging conditions. The battery can be charged by the power received from the solar panels in the dawn and while in the dusk it charges the battery.
PWM (Pulse Width Modulation)
- The term duty cycle describes the proportion of on time to the regular interval or period of time; a low duty cycle corresponds to low power because the power is off for most of the time.
- Duty cycle is expressed in percent, 100% being fully on.
- The main advantage of PWM is that power loss in the switching devices is very low. When a switch is off there is practically no current, and when it is on, there is almost no voltage drop across the switch.
- PWM works also well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle.
- The longer the switch is on compared to the off periods, the higher the power supplied to the load is.
MOSFET (IRF 510)
- The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a device used for amplifying or switching electronic signals.
- The basic principle of the device a voltage on the oxide-insulated gate electrode can induce a conducting channel between the two other contacts called source and drain.
- It is by far the most common transistor in both digital and analog circuits, though the bipolar junction transistor was at one time much more common.
- Internally frequency compensated for unity gain
- Large DC voltage gain 100 dB
- Wideband with 1Mhz (Temperature compensated)
- Wide power supply range:
- Single supply 3V to 32V or dual supplies ±1.5V to ±16V
- Very low supply current drain (700 μA) essentially independent of supply voltage
- Low input biasing current 45 nA (temperature compensated)
- Low input offset voltage 2mV and offset current:5 nA
- Large output voltage swing 0V to V+ − 1.5V
BC547 (NPN –Transistor)
- The BC547 transistor is an NPN Epitaxial Silicon Transistor.
- It is used in general-purpose switching and amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors.
- The ratio of two currents (Ic/Ib) is called the DC Current Gain of the device and is given the symbol of hfe or nowadays Beta, (β).
- The current gain from the emitter to the collector terminal, Ic/Ie, is called Alpha, (α), and is a function of the transistor itself.
- The 1N4148 is a standard small signal silicon diode used in signal processing.
- The 1N4148 is generally available in a DO-35 glass package and is very useful at high frequencies with a reverse recovery time of no more than 4ns.
- This permits rectification and detection of radio frequency signals very effectively, as long as their amplitude is above the forward conduction threshold of silicon (around 0.7V) or the diode is biased.
- Photovoltaic (PV) cells are made of special materials called semiconductors such as silicon, which is currently the most commonly used.
- Basically, when light strikes the cell, a certain portion of it is absorbed within the semiconductor material.
- PV cells also all have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction.
- This flow of electrons is current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off to use externally.
- Expose the cell to light, and the energy from each photon (light particle) hitting the silicon, will liberate an electron and a corresponding hole.
- If this happens within range of the electric field’s influence, the electrons will be sent to the N side and the holes to the P one, resulting in yet further disruption of electrical neutrality
- This flow of electrons is current; the electrical field in the cell causes a voltage and the product of these two is power.
Working with Project
- The solar panel is a current source is used to change battery B1 via D10. While the battery is fully charged the voltage at cathode point of D10 goes up. This results in the set point voltage at pin 3 of U1: A to go up above the reference voltage because the potential divider formed out of R12, 5K variable resistor, R13 goes up.
- This results in pin no 1 of U1: A to go high to switch ‘ON’ the transistor Q1 that places drive voltage to the MOSFET IRF640 .such that the current from solar panel is bypassed via D11 and the MOSFET drain and source
- Simultaneously pin 7 of U1: B also goes high to drive a led D1 indicating battery is being fully charged
- Whenever the solar charge is low the circuit utilizes the power from the battery, if the battery goes into deep discharge, then it utilizes power from solar power then the Led’s flashes light.
Thus, this is all about Solar Powered Led Street Light with Auto Intensity Control. We hope that you have got a better understanding of this concept. Furthermore, any queries regarding this concept or to implement solar-based projects, please give your feedback in the comment section below. Here is a question for you, what is the function of a solar panel?